fix GMP compilation problems for RPI

.github/resources/prover/Makefile

@@ -34,7 +34,7 @@ host_linux_aarch64_static:
 	    -DCMAKE_CXX_COMPILER=aarch64-linux-gnu-g++ \
 	    -DCMAKE_EXE_LINKER_FLAGS="-static -static-libstdc++ -static-libgcc -no-pie" \
 	    -DUSE_ASM=OFF \
-	    -DCMAKE_PREFIX_PATH=depends/gmp/package_aarch64 && \
+	    -DGMP_PREFIX=depends/gmp/package_aarch64 && \
 	make -j$(nproc) -vvv && make install
 
 host_windows_x86_64_static:

.github/resources/witness-generator/Makefile

@@ -20,9 +20,11 @@ linux: LDLIBS=-lgmp
 linux: $(BIN)
 
 # ---- Linux aarch64 (cross-compile) ----
+# Uses GMP built in rapidsnark/depends/gmp/package_aarch64
+# Path is relative from circuit_cpp directory (e.g., mantle/pol_cpp/)
 linux_aarch64: CXX=aarch64-linux-gnu-g++
-linux_aarch64: CXXFLAGS=$(CXXFLAGS_COMMON)
-linux_aarch64: LDFLAGS=-static
+linux_aarch64: CXXFLAGS=$(CXXFLAGS_COMMON) -I../../rapidsnark/depends/gmp/package_aarch64/include
+linux_aarch64: LDFLAGS=-static -L../../rapidsnark/depends/gmp/package_aarch64/lib
 linux_aarch64: LDLIBS=-lgmp
 linux_aarch64: $(BIN)
 

.github/workflows/build-circuits.yml

@@ -416,7 +416,7 @@ jobs:
         run: sudo apt install -y build-essential cmake libgmp-dev libsodium-dev nasm curl m4
 
       - name: Install Dependencies [Cross-compilation]
-        run: sudo apt install -y gcc-aarch64-linux-gnu g++-aarch64-linux-gnu libgmp-dev:arm64 || sudo apt install -y gcc-aarch64-linux-gnu g++-aarch64-linux-gnu
+        run: sudo apt install -y gcc-aarch64-linux-gnu g++-aarch64-linux-gnu
 
       - name: Install Dependencies [Witness Generator]
         run: sudo apt install nlohmann-json3-dev